This invention relates to transplantation therapies and, in particular, to novel compositions and methods for reducing the incidence of transplant rejection reactions and graft versus host disease.
Transplantation therapy is known whereby bone marrow or tissue, e.g., an organ, from a donor is infused into or grafted to a recipient. However, because of the frequency of life-threatening rejection reactions such therapies have only limited use. Typically such therapies are attempted only where the person's prognosis without transplantation therapy is exceedingly poor.
For example, bone marrow transplantation is currently limited to patients with severe, life-threatening diseases such as leukemia, aplastic anemia, and congenital immunodeficiency disease. For the success of the procedure, it is essential that the donor and recipient be matched by tissue typing tests including human leukocyte antigens (HLA) and mixed leukocyte culture (MLC). This matching requirement severely limits the number of patients who are even candidates for the procedure. The chances of finding an appropriate donor in the general population is exceedingly remote, although there has been an effort to tissue type large numbers of potential donors and provide matched tissues for recipients. More commonly the donor is a family member, but even then, the chances of finding a sibling who is matched with the patient is only one in four, and the chances that other family members will match the patient is considerably less.
The problem which occurs in bone marrow transplantation when donor and recipient are not matched, i.e. are allogenic, is that the transplanted cells of the donor recognize the recipient as foreign and attempt to reject the recipient's tissue, producing a condition termed graft versus host disease (GVHD). This results in skin rash, intestinal disease, and liver disease. These manifestations of GVHD may be severe and may lead to death. In patients with advanced GVHD, only 15% survive.
To perform a bone marrow transplant, one first locates a matched donor. It is necessary to render the recipient immunologically incompetent, i.e., to incapacitate the recipient's natural immunological system, so that he will not reject the donor marrow. This is done by the use of high dose total body radiation, chemotherapy, or a combination of the two. Marrow is obtained from the matched donor under general anesthesia in the operating room. This is done by inserting needles into the marrow cavity and aspiration of the marrow. Marrow is passed through screens to separate cells and then administered to the recipient intravenously or intraperitoneally.
A number of attempts have been made to get around the necessity of matching donor and recipient to avoid the development of GVHD. It is believed that GVHD is caused by the presence of mature thymic-derived lymphocytes (T cells) in the bone marrow preparation. It is believed that the more immature stem cells in the bone marrow are responsible for reconstitution of the recipient marrow and that they do not cause GVHD, probably because they are "educated" in the recipient and do not recognize the recipient as foreign.
Various approaches have been attempted in experimental animals whereby the mature T cels in the donor bone marrow are eliminated, and the recipient animal is reconstituted only with stem cells. Dicke et al. (1968) taught the separation of mature cells from stem cells using a discontinuous albumin gradient and demonstrated that these stem cells could reconstitute in irradiated mice without causing GVHD. Cantor (1972) teaches treatment of parental spleen or lymph node cells with anti-theta (antibody to T cells) and complement whereby GVH activity in the mouse is abolished.
Muller-Ruchholtz et al. (1976) disclose that by treating donor rat bone marrow cells in vitro with cytotoxic anti-lymphocyte sera (ALS) which had been made specific for mature T cells and pre-T cells by absorption, successful reconstitution of the cells in lethally irradiated rats across a strong histocompatibility barrier could be accomplished without GVHD.
The use of lectins peanut agglutinin (PNA) and soybean agglutinin (SBA) to fractionate murine bone marrow and spleen cells is known. Receptors for these lectins are present on the surface of immature thymocytes, and as such immature thymocytes can be isolated from bone marrow and spleen by agglutination with PNA and SBA. The immature or stem cells thus agglutinated were shown capable of reconstituting irradiated animals without production of GVHD.
Nevertheless, bone marrow transplantation is an experimental therapy which is only marginally successful at the present time. In only a minority of the patients is a matched donor available. Even with a matched donor, there are numerous complications. GVHD may develop, and survival is poor. The majority of patients lack a matched donor, and therefore bone marrow transplantation under the circumstances is not even a consideration. There have been only a few reports of successful reconstitution of bone marrow with tissue from an unmatched donor. The technique we propose will permit successful transplantation of donor marrow from unmatched donors without production of GVHD.
For transplantation of organs, such as kidney or heart, it is not essential that the donor and recipient be matched. In this circumstance, GVHD is not a problem, but an unmatched organ will be rejected by an immunocompetent recipient, i.e. a recipient capable of producing antibodies. To avoid rejection of the transplanted organ from an unmatched donor, to date it has been necessary to treat the recipient with immunosuppressive therapy. This usually consists of treatment of the recipient with azathioprine and a corticosteroid or cyclosporin. This type of immunosuppressive therapy produces broad suppression of all immune responses, including those to infections, and can lead to severe, life-threatening complications. Results of cadaveric renal transplantion vary, but at some centers, less than 40% of such transplants survive one year. Survival is less for heart transplants, and considerably less for transplants of other organs such as liver or lungs.
Among organ transplantion, that of kidneys is presently a useful therapeutic technique. Nonetheless, tissue typing is important, and results are less satisfactory if the donor and recipient are not well matched. Recipients of kidney transplants generally require administration of immunosuppressive agents which can produce serious complications, especially susceptibility to infectious diseases. Transplantation of other organs is highly experimental and not very successful because of the rejection process.
An object of the present invention are compositions and methods to improve organ transplantation and to permit transplantation of bone marrow from donors not necessarily matched to the recipient by tissue typing by specifically killing cells involved in the rejection process.
A still further object is to provide a method of bone marrow transplantation to provide a therapy for the following conditions:
a. Leukemia and other malignancies since it would permit use of extraordinarily large doses of radiation and/or chemotherapy.
b. Hematologic abnormalities such as sickle cell anemia, aplastic anemia, and others in which one of the elements of the blood is abnormal or in which the bone marrow is not functioning properly.
c. Congenital or acquired immunodeficient diseases such as severe combined immunodeficiency disease, chronic mucocutaneous candidiasis, the Wiskott-Aldrich Syndrome, and others in which the immune system is not functioning properly.
d. Nuclear holocaust, in which the bone marrow is destroyed and transplantation of marrow would be life-saving.